It is known that unsubstituted 1,3-cyclopentadiene reacts with a metallic sodium to produce a sodium salt of cyclopentadienyl anion (sodium cyclopentadienylide) (see K. Hafner and H. Kaiser, Org. Syn. Coll., vol. 5, 1088 (1973) and R. B. King and F. G. A. Stone, Inorg. Syn. 7, 99 (1963)).
Further, it is known that a disubstituted 1,3-cyclopentadiene reacts with butyllithium (BuLi) to produce a lithium salt of cyclopentadienyl anion (disubstituted lithium cyclopentadienylide) (see Japanese Patent Laid-open Publication No. 63(1988)-222177).
Still further, it is known that a pentasubstituted 1,3-cyclopentadiene reacts with BuLi to produce a lithium salt of cyclopentadienyl anion (pentasubstituted lithium cyclopentadienylide) (see JACS, 100, 3078 (1978)).
Conventionally, the anionization of a disubstituted or trisubstituted cyclopentadiene is performed by the reaction with an alkyllithium such as butyllithium (BuLi), and no other method has been known. This anionization of a disubstituted or trisubstituted cyclopentadiene by the reaction with an alkyllithium must be carried out at low temperatures such as -78 to 0.degree. C., so that the temperature control is not easy. Further, the alkyllithium is expensive and is difficult to handle in the air. Still further, there are disadvantages such that the upper limit of the concentration of butyllithium which is available in the market is as low as 2 mol/lit., so that desirably high efficiency of a reaction vessel cannot be attained.
Therefore, the inventors have made extensive and intensive studies with a view toward solving the above problem. As a result, it has been found that sodium hydride (NaH) which is inexpensive and is easy to handle in the air reacts with a disubstituted or trisubstituted cyclopentadiene at room temperature to about 150.degree. C. so that the disubstituted or trisubstituted cyclopentadiene are anionized to enable obtaining sodium cyclopentadienylides with high yield, generally at least 85%. The present invention has been completed on the basis of this finding.